Carburetor



Om O mm. .ONN mhm Nwm 0mm wwm Nhm INVENTOR Jan. 23, 1968 R. c. LA FORCE CARBURETOR 5 Sheets-Sheet 1 Filed July 12, 1966 Robert CjLoForce Jan. 23; 1968 R. c. LA FORCE CARBURETOR 3 Sheets-Sheet 3 Filed July 12, 1966 Ohm wmm mwm wwm NwN INVENTOR.

Robert C. LuForce BY 9/ United States Patent G M 3,365,179 CARBURETGR Robert C. La Force, Beaver, Pa., assignor of one-third to Sherwood N. Webster, Washington, D.C., and one-third to John Kaufmann, In, Pittsburgh, Pa.

Filed July 12, 1966, Ser. No. 564,636 31 Claims. (Cl. 26139) ABSTRACT OF THE DISCLOSURE A carburetor having a wide range of automatic adjustments in the admittance of fuel or in the admittance of secondary or by-passing air or both is disclosed. A secondary air valve is actuated by venturi or manifold pressures or both. A secondary fuel valve is similarly actuated. In one arrangement the air valve is controlled by pressure sensitive motive means actuated by manifold depression in opposition to tandem biasing springs to provide variable control of the air valve in differing ranges of manifold depression. The motive means may operate in parallel with second motive means controlled both by venturi and manifold depressions. The air valve normally is prevented from complete closing by a restraining member. However, linkage may be connected to the choke mechanism for de-activating the restraining member to permit complete closure of the air valve upon closure of the choke mechanism.

This invention relates: generally to carburetors for internal combustion engines and certain features thereof are specifically directed to improvements in the carburetor described in my Patent No. 3,182,976, issued May 11, 1965. More particularly, the invention is directed to a carburetor capable of producing an optimum fuel-air mixture under all operating conditions of such engines.

Conventional carburetors particularly for use with engines employed in passenger vehicles have been the subject of considerable design and engineering effort in order to provide a reasonable balance of fuel to air under all operating conditions of the engine. However, the best carburetors presently available do not provide means for sufliciently varying the fuel to air admixture under all operating conditions. As a result, the engines provided with such carburetors exhibit, for example, poor idling characteristics with the result that such engines must be set at too fast idle speeds which are wasteful of fuel.

Another disadvantage of conventional carburetors is their inability to provide an optimum fuel to air admixture at low speed power demand conditions of the associated engine. Conventional carburetors employ a fuel enrichment valve to admit additional or auxiliary fuel into the main fuel line which opens into the inner or booster venturi usually employed therein. However, the fuel enrichment valve and associated by-passing fuel channel are sized for a maximum power demand condition, for example, high speed maximum or near maximum acceleration. As a result, for most low speed accelerating conditions, the carbureted fuel-air mixture is over-enriched and is likewise wasteful of fuel.

As mentioned previously, most engines, when provided with conventional carburetors, exhibit rough idle conditions and thus the carburetor must be adjusted in order to provide a too-rapid idle in order to prevent stalling, and to attain a tolerable smoothness of operation. The lack of desirable engine smoothness at idling speeds is particularly disadvantageous when the engines are used in vehicles with automatic transmissions where the engine canot be de-clutched from the transmission and therefore is always under some load. In accordance with another feature of the novel carburetor, means are associated with the throttle valve or plate thereof to en- 3,365,179 Patented Jan. 23, 1968 sure thorough mixing of the fuel and air under either hot or cold engine conditions. Such thorough mixing has not been heretofore made possible and the absence of such thorough mixing is responsible for rough idle conditions.

A further and much more hazardous disadvantage of such over-enriched fuel mixtures produced by conventional carburetors, is the production of noxious gases from the resultant inefficient and incomplete combustion of the fuel. The engine exhaust at such times includes an abundance of the well-known and highly-poisonous carbon monoxide and other harmful organic gases.

The production of noxious exhaust gases is particularly noticeable and undesirably accumulative in city trafiic and other confining or restrictive locations, where a large number of vehicles in relatively slow moving trafiic are subjected to continuous, low speed, accelerations or decelerations.

During the aforementioned low speed accelerating conditions, conventional carburetors are incapable of properly selecting fuel flow patterns consistent with the minimal air requirements at such times. This results from the use in conventional carburetors of power enrichment valves which are opened by spring action assisted by manifold pressure acting on a diaphragm or piston. Such valves are restrained from opening my atmospheric pressure, sometimes assisted by a second, much lighter spring than the first and tend to open more readily at high elevations which premature opening taken in conjunction with the rarefied atmosphere attendant with high elevations tends to over enrich the power mixture. Furthermore, manifold pressure increases as the throttle is opened by the driver operator who has no conceivable way of knowing the fuel needs of an engine at any speed or load condition. Such conventional power enrichment valves yield excessive fuel-air ratios during low speed accelerations in response to excessive throttle openings by impatient, heavyfooted drivers.

This is compounded by the use in conventional carburetors of compromised venturis and carburetor throat sizes in an attempt to establish an average structural relationship of the carburetor to meet all engine conditions of speed and power. For exam-pie, the carburetor venturis on the one hand desirably should be provided with a small throat or constriction for optimum fuel mixing or carburetion but on the other hand desirably should be provided with a large throat of little constriction to provide adequate air at maximum or near-maximum engine speeds. Conventional carburetors utilize venturis which are a compromise between these opposing size determinations. As a result, conventional carburetors provide less than optimum fuel and air mixing on the one hand and on the other permit engine starvation for Want of air at maximum engine speeds owing to the use of the compromised venturis.

The inadequate fuel-air supply at high engine speeds, moreover, becomes over-leaned by conventionally provided carburetor means for supplying additional fuel under maximum or near-maximum power demands at such speeds. The over-leaned fuel mixture is wasteful of fuel since the vehicle operator tends to increase the input of the inefficient fuel mixture to the engine. Obviously, the over-leaned mixture also decreases the power output of the engine, particularly when the speed and power conditions of the engine approach the point where the engine begins to starve as a result of insuflicient air.

As pointed out above, conventional carburetors are, of course, provided with means for varying the fuel-air ratios under differing operating conditions. However, such means are subject to driver selection and are generally characterized by full on or full off operation such that the change in fuel-air ratio is sudden and at best represents a compromise condition, with the result that the engine either wastes fuel or sacrifices power and performance or both. Moreover, conventional ratio adjustment means of known carburetors are in general insensitive to incoming air temperatures, with the result that the carburetor requires frequent adjustment for seasonable climatic conditions. For daily or day-to-day temperature differences, however, it is inconvenient and hence impractical to make the required carburetor adjustments. Hence, conventional carburetors are wasteful of fuel and engine performance for this reason also.

In overcoming these difiiculties of the prior art, I provide a carburetor having one or more barrels in which the venturis desirably are sized for optimum air-fuel mixing characteristics. In order to compensate for the unusually small size of the venturis, a by-passing or secondary air channel is provided for admitting such air downstream of the venturis. There is also provided means for carefully metering the bypassing air in response to intake manifold and venturi depression conditions, which are indicative of engine speed and power conditions. The control mechanism for such metering means is counterbalanced in accordance with another feature of my carburetor in a novel manner by these indicators and associated components to provide a smooth variation in fuel to air ratio with attendant variation over a wide range of engine operating conditions.

In accordance with another feature of my carburetor, means are coupled to the aforementioned secondary air metering means and to an otherwise conventional choke mechanism for causing the secondary air metering means to close the secondary air channel during cold starting or cold engine running conditions. Control of the secondary air channel is relinquished to the secondary air metering means by the choke mechanism when the latter approaches or reaches its full-open condition. If desired, means forming part of the novel choke mechanism can be arranged to delimit the metering action of the secondary air control means such that a relatively small flow of secondary air is maintained at all times through the bypassing air channel. Such minimum flow compensates for the unusually small sizes of the venturis during periods of minimal engine power demands and also imparts additional atomization to the fuel leaving the venturis. The minimal air flow also prevents the development of flat spots in carburetion when the secondary air flow is increased.

In accordance with another feature of the carburetor, the secondary air control mechanism is arranged to increasingly restrict the flow of secondary air in order to produce optimum and appropriately varyingly enriched fuel-air mixtures as engine power demands increase. However, at maximum or near-maximum engine power conditions, still another feature of the secondary air control mechanism provides increasing amounts of by-passin g air as engine power demand increases beyond the point where the engine would otherwise begin to starve for lack of air. At this time secondary fuel control means of the invention also are variably actuated to supply the required increasing amounts of additional fuel.

The novel carburetor construction is provided with a primary power enrichment valve of correspondingly reduced fuel flow capacity for engine power demands at relatively low speeds. In accordance with another feature of my carburetor, however, the aforementioned secondary fuel metering means are utilized in tandem with the primary power enrichment valve in order to smoothly introduce controlled amounts of fuel to maintain the optimum fuel-air power mixture during the transition from low speed power to maximum or high speed power re quirements. In the example described herein, the fuel metering device is placed in tandem with the primary power enrichment valve and communicates directly therewith so that close tolerances and fits are not essential to its operation. However, it is also contemplated that the fuel metering device can be placed in parallel with the conventional power enrichment valve, with the latter being made smaller in size for independent operation.

In one arrangement of my carburetor, the fuel metering means are arranged for actuation by the depression conditions of the intake manifold and of the venturis, in somewhat the same manner as the aforementioned secondary air control mechanism. It will be understood, therefore, that the fuel meteing means and the secondary air metering means are thus coordinated by the aforementioned carburetor depressions. Although separate control mechanism are so coupled as illustrated in the drawings, it will be understood that a common control mechanism can be used to control both the operation of the secondary air metering means and of the auxiliary fuel metering means.

The aforementioned and briefly described carburetor improvements provide an optimum, and therefore economical, fuel-air ratio for each of the many and varied engine operating conditions of speed and power requirement. Inasmuch as an optimum and varying fuel-air ratio is provided by the novel carburetor disclosed herein at all times, the fuel combustion, moreover, is substantially complete at all times with result that noxious exhaust gases are virtually eliminated. Accordingly, with the carburetor of the invention it is not necessary to equip the engine exhaust with auxiliary anti-air pollution devices, as required by law in some localities. On the other hand, maximum or near-maximum engine performance is not sacrificed by the necessity of providing, as in a conventional carburetor, a few averaged and compromised fuelair mixtures available respectively for wide ranges of engine conditions.

The novel carburetor is illustrated and described in detail hereinafter primarily as a dual-barrel carburetor, although it will be readily understood that the novel control features disclosed herein can be applied readily to a single-barrel or to a multiple-barrel carburetor, as desired. In summary, the novel carburetor disclosed herein provides a fuel economy which is greater than that possible with either a single or dual-barrel conventional carburetor, while at the same time making available in a single or dual-barrel carburetor the engine speed and performance characteristics of a four-barrel carburetor. However, the initial expense, the difiiculties of maintenance and adjustment, and the poor fuel economy of the latter type of conventional carburetor are eliminated by the invention.

During the foregoing discussion, certain objects features and advantages of the invention have been set forth. These and other objects, features and advantages of the invention, together with structural details thereof, will be elaborated upon during the forthcoming detailed description of certain presently preferred embodiments of the invention together with preferred methods of practicing the same.

In the accompanying drawings, I have shown certain presently preferred embodiments of the invention and have illustrated certain presently preferred methods of practicing the same, wherein:

FIGURE 1 is a side elevation view of one form of carburetor arranged in accordance with the invention, with parts thereof being broken away and other parts being sectioned generally along reference line I-I of FIGURE 3, in order to show the invention more clearly; the carburetor components are positioned as required by moderate power demands of an associated engine (not shown);

FIGURE 1A is a partial view of FIGURE 1 showing the position of the secondary air control mechanism components when the engine is stopped but warm or is subjected to comparatively light power requirements;

FIGURE 2 is a partial, sectional view of the carburetor as shown in FIGURE 1 and taken along reference line II-II thereof;

FIGURE 3 is a top plan view of the carburetor as shown in FIGURE 1, with parts thereof being broken away in order to illustrate the invention more clearly;

FIGURE 4 is a side elevational view of a fuel metering plate forming part of the carburetor and designated by the reference character 162 in FIGURE 1; and

FIGURE 5 is a cross-sectional view of the metering plate shown in FIGURE 4 and taken along reference line V-V thereof.

Referring to the drawings there is illustrated a carburetor having an enclosed air chute 12 aflixed between the main body or carburetor block 11 and throttle base 14 which is bolted together with a fibrous insulating block 15 to the manifold of an engine 16 shown in fragmentary form. The air chute 12 is enclosed by vertical sides 18 so as to provide a closed fiowpath denoted by arrows 20 for the transmission of clean air from filter 22 to secondary flow channel denoted by arrow 23. The secondary flow channel 24 communicates directly with main throat 26 of the carburetor between throttle valve and venturi 28 having an unusually restricted throat section 29 and the usual booster venturi 31 therein. The more restricted venturi 28 of the invention provides a greater fuel-air mixing or carbureting etficiency at lower motor speeds. However, the restricted venturi 28 does not admit sufficient air at higher motor speeds and hence the use, in accordance with the invention, of the secondary or bypassing channel 24 and associated controls are described in detail below. The secondary flow channel 24 provides access to the carburetor throat 26 at a convenient location for the co-mingling of filtered atmosphere with a carbureted mixture from the over-rich venturi 28 as denoted by flow arrows 33 and described and claimed in my aforesaid patent.

Throttle valve 30 is made initially in the usual manner; for example, if designed to be substantially fully closed when rotated 80 from the axis of the throat 26, then it is preferably sheared in the form of a 10 elipse such as might be described by transversely cutting a piece of round bar stock of similar diameter at an angle of 10 from the perpendicular then by cutting a wafer of throttle plate thickness off the same end parallel to the first cut. Such is the shape of conventional throttle plates which are made to fit equally well on all sides of the bore when the throttle is closed. In accord with one feature of the instant invention, the throttle plate 30 is attached to throttle shaft 32 by screws 34, and thence to the conventional accelerator linkage 33 and related components as shown in FIGURE 3. The throttle plate is modified by bending upward on the fuel feed side, denoted by reference character 35 in FIGURE 1, in the neighborhood of 5-10", for example 7 at bend line 36. Desirably, the conventional low speed fuel outlet 37 is raised accordingly to maintain a relative optimum operating position with the low pressure area at the adjacent, cooperating edge of the up-bent throttle plate and to achieve the novel results of the invention as set forth below. The degree of the bend will, of course, be varied in accord with power requirements of a particular engine at its idling operation.

The conventionally provided vacuum spark advance channel (not shown) is similarly raised or throttle shaft 32 may be dropped a similar amount, instead, to compensate for the up-bent throttle plate 36.

The novel throttle plate 30 is thus fully closed at the rear edge 40 during idle under normal conditions and admits the usual amount of normally by-passing air but only at or near the front or fuel edge 38 for a much smoother and more economical idle. The novel construction and design of throttle valve 30 provides a more etficient idle-fuel admixture standing alone in comparison to conventional throttle valves inasmuch as all or substantially all of the idle air flow is directed by the upbent throttle plate 30 past the idle fuel inlet at optimum idle adjustments. Moreover, the up-bent front side displays the operating characteristics of a conventional 14 throttle plate but provides more opening per degree of shaft rotation on the fuel side while the rear side displays the operating characteristics of a conventional 7 throttle plate since the up bent throttle plate 30 is fully closed on its rear side at idle and does not require the initial idle opening of about 3 as in conventional, completely flat throttle plates. The rear side of the throttle plate 30 is thus retarded in opening per degree of throttle rotation while the front or fuel side is advanced which lessens the air-flow velocity more quickly and thereby causes the low speed fuel flow to diminish earlier as the throttle is opened.

This throttle plate 30 arrangement also cooperates with the more restricted venturi 28 of the invention and compensates for the earlier fuel flow normal thereto and also provides for more eflicient idle and low speed mixture. A flow adjusting valve 42 is located in the upper wall structure 44 (as viewed in FIGURE 1) of the secondary flow channel 24 for controlling the flow of secondary or by-passing air to the carburetor 10 in response to controlling devices provided in accordance with the invention and described in detail hereinafter. The valve 42 is carried on a rotatably mounted spindle 46 suitably journaled in the upper wall structure 44 of the air channel 24. The valve 42 has its free or effective end extending generally longitudinally downstream of the spindle 46. The flowadjusting valve 42 includes, in this example, an integral operating arm 48 extending in the opposite direction of the spindle. Means described below are provided for manipulating the arm 48 in a carefully controlled manner and hence for similarly operating the valve 42 to control the flow of air through the channel 24.

The forward or effective end of the valve 42 is provided with an arcuate and upwardly directed lip 50 which extends upwardly into a Well 52 in channel wall structure 44. The outer arc of lip 50 is subtended immediately adjacent one wall of well 52 with clearance sufficient to prevent friction, yet with proximity sufficient to prevent carburetor throat depression or vacuum operating through channel 24 from acting on the upper surface of valve 42; the valve well 52 is provided with a vent 54 to prevent such carburetor throat depression from building up behind the valve 42 through such clearance. The valve 42 is urged toward its channel-closed position by coil spring 56 or other suitable biasing means seated in a suitable recess in upper wall structure 44 and acting downwardly on the upper surface of valve 42.

The arcuate valve lip 50 thus renders control valve 42 insensitive to carburetor throat pressure variations, while the biasing spring 56 urges the valve 42 toward its channel-closing position to the limits allowed by the aforementioned control devices presently to be described.

Mounted within the confines of air cleaner 22 and the enclosing walls 18 of air chute 12, in this example, a dual-pressure sensitive control mechanism denoted generally by reference character 58 is secured by mounting bolts 60 holding its flange 62 to angle brackets 64 which in turn are secured to opposite side walls 18 of chamber 12 by bolts 66. The control mechanism 58 is divided into a pair of longitudinally extending cylindrical chambers 67 and 69 in the side Walls of which are formed longitudinally extending and generally transversely aligned slots 68, 70 and 72 respectively to accommodate the control arm 48 of the valve 42. The control mechanism 58 contains, in this example, two generally cylindrically-shaped control devices or pistons 74 and 76. The control devices 74 and 76 are closely and slidably fitted in the chambers 67 and 69, respectively, and have connecting rods 78 and 80 which are also slotted at 79 and 81 respectively so as to straddle control arm 48 as better shown in FIGURE 1.

The control piston 74 is responsive to manifold vacuum or depression which is communicated thereto via conduit 82 secured to carburetor block 11 at passage 250 therein described below and connecting passages 83 and 85. In response to idle vacuum, illustrated and described exemplarily herein as 20 inches of mercury, in the lower end 84 of chamber 67, the piston 74 and connecting rod 78 are urged downwardly thereby causing contact 86 of the slotted connecting rod 78 to engage operating arm 43 and thus rotate spindle 46 and valve 42 to its presently shown idle or light cruise position. Opposite threaded end 88 of the connecting rod 78 is slidably extended through stationary annular spring seat 9%) formed within the inner walls of cylinder 67 which serves as a base for coil spring or other biasing means 92, annular seat 93 of slidably mounted tubular spring divider or retainer 94, counterbiasing spring retainer or means 96, and the outer end 97 of the spring housing 98, where the connecting rod 78 is adjustably secured thereto by lock nuts 100 and 102. The spring retainer 94 and the spring housing 98 are slidably mounted within an adjustable tubular guide 164 which in turn is threaded in the mechanism block 59, where it can be locked in a desired position of adjustment by a suitable lock screw 103 (FIGURE 3). The movement of the spring retainer 94, which divides the tandem biasing springs 92, 96 is delimited by stationary stops 95 and 110. On the other hand the range of movement of spring housing 98 includes that of the spring retainer or divider 94 plus the width of gap 107 (FIGURE 1A), since retainer 94 is moved by the spring housing 98. Thus, control piston 74. is moved by manifold depression first against the biasing force of the lighter upper spring to close gap 197 and then against the heavier lower spring 92 to close the gap between the lower end 108 of the spring retainer 94 and its lower stop 110, for the purposes described in greater detail below.

The bore of the adjustable guide 104 is expanded ad jacent the inner end thereof to engage an exterior circumferential shoulder 166 of the spring retainer 94 at its outer limit of travel as shown in FIGURE 1, and in this example, the guide 104 is threaded into the block 59 and its chamber 67 to the extent that the spring 92 is preloaded to balance 20 inches of mercury manifold depression acting as aforesaid upon control piston 74. Movements of the spring retainer or divider 94 in response to decreases in manifold depression are thus delimited by inner shoulder 95 on the guide 104 in the upper direction as viewed in FIGURE 1 and in the opposite direction, in response to increases in manifold depression, such movements are delimited by the upper surface of chamber shoulder 110.

The spring housing 98, on the other hand, is secured to connecting rod 78 for sliding movement therewith and depending upon the depression conditions in the manifold 16, the spring 96 variously opens gap 107 between the spring retainer 94 and spring housing 98, with such gap being shown adjacent closed position in FIGURE 1, which occurs in this example at about 20 inches of mercury depression, as normally experienced during idle or light cruise conditions.

With the engine off, spring 96 is normally expanded from its position in FIGURE 1 thereby raising spring housing 98 away from retainer 94 so that gap 107 is expanded to its position as shown in FIGURE 1A and becomes equivalent to the gap illustrated in FIGURE 1 between shoulder 105 and seat 90. At the same time shoulder 16S, carrying with it shaft 88, is raised to a seated position against seat 90 (FIGURE 1A) by virtue of spring housing 98 being urged upwardly against nuts 109 and 102. Adjusting and locking nuts 100 and 102 have been previously manipulated on the adjacent threaded portion 88 of the associated connecting rod 78 in order to position the spring housing 98 relative to connecting rod 73 so as to adjustably preload the counterbiasing spring 96 to counterbalance about five inches of mercury manifold depression acting on control piston 74. The length of spring housing 98 has been previously calibrated so as to develop the correct width of the gap 107 when expanded (FIGURE 1A) as previously described in conjunction with the desired preloading of spring 96. Spring 95 is expanded in the manner just described during heavy accelerations of the engine and thus is preloaded to counterbalance about five inches of mercury depression acting on control piston '74 so as to retract contact away from control arm 43 and to urge shoulder 195 against seat (FIGURE 1A) with retentive energy sufficient to ensure the counterbalancing of residual manifold depressions of two to three inches normally experienced during such heavy accelerations.

The accompanying movement of the connecting rod 78 manipulates arm 43- to substantially close the by-passing air channel 24. The spring 9-5 is properly selected and calibrated as noted above so that it will be moved progressively to its illustrated position of compression as shown in FIGURE 1, closing the gap 197 between the spring housing 98 and the spring retainer 94 at about 15 inches of mercury manifold depression or vacuum during light cruise and so that the spring 95 can move oppositely to its fully expanded position, thereby seating shoulder 1535 against seat 90 as during subsequent heavy accelerations.

With this arrangement, the piston 74 and valve 42 will remain dormant or in their normal disposition, as shown in FIGURE 1, during vehicle cruising and light accelerations over a range of manifold depression readings from about 15 inches of mercury down to about 20 inches of mercury due to the retentive energy of the preloaded biasing spring 92. However, during medium vehicle accelerations for power, at manifold depression readings of from about 15 inches of mercury down to about 5 inches of mercury, the counterbiasing spring 96 will expand, sliding the spring housing 98 and connecting rod 78 upward within the pre-adjusted tubular guide 194 drawing connecting rod contact 86 away from the valve operating arm 48. The arm 48 will then follow by virtue of expanding spring 56 and will move valve 42 toward a more closed or richer setting thereof to restrict the flow of secondary air through channel 24 and to reduce the air component of the air-fuel mixture as required.

On the other hand, at manifold depression readings of, for example, from about 20 inches of mercury down to about 25 inches of mercury, encountered during vehicle decelerations, the spring 92, will yield, and the spring retainer 94 and spring housing 98 both will slide downwardly within the tubular guide 104 pulling connecting rod contact 86 against valve operating arm 48 thereby rotating the air channel valve 42 against spring 56 so as to open valve 42 thereby leaning out the air-fuel mixture to conserve fuel during decelerating conditions. Following the foregoing specific example, upon a maximum deeleration, for example to about 25 inches of mercury, spring housing 98 urges spring retainer 94 against the biasing spring 92 until lower end 198 of the spring retainer 94 engages the upper surface of the chamber shoulder 11!) as a stop to prevent excessive opening of the valve 42.

It will be obvious that each of the above operations are reversible when the aforementioned vacuum depression conditions are encountered in the opposite direction during vehicle operation. It should also be noted that springs 92 and 96 both cooperate to remove connecting rod contact 86 upward and out of contact with its valve control arm 48 when the vehicle engine is shut off, so that valve arm 48 can move upward under impetus of spring 56 either to a minimum closed position or to a full choke position of the valve 42 under the control of other novel means of the invention, as described in greater detail below.

The mixture control piston 74 is employed to adjust valve 42 throughout the normal driving range of light cruise, deceleration and medium acceleration up to the point of maximum manifold pressure at which point springs 92 and 95 retract contact 86 up and away from control arm 48 thus permitting the valve 42 to move to ward a more closed position under impetus of spring 56 to restrict the tlow of secondary air past valve 42. This serves well to enrich the mixture but also transfers the burden of supplying air almost completely upon the limited flow capacity of restricted venturi 28.

The enriching response of secondary air channel valve 42 to increase in manifold pressure is highly advantageous even during high speed when accompanied by moderate power requirements. However, under high speed conditions accompanied by maximum or near maximum power requirements a point is reached where the restricted venturi 28 becomes overburdened. In accordance with another feature of the invention, then, means presently to be described are provided for re-opening the valve 42 under such maximum or near maximum power requirements to prevent the engines starving for lack of sufiicient air. At the same time means, also hereinafter described, are provided for controlling the flow of fuel to the carburetor to provide the proper air-fuel mixture.

By way of background it should be noted that the ventun's as employed in conventional carburetors are of necessity a compromise, that is to say, they are not large enough for maximum power requirements, but are not small enough for optimum fuel mixing and maximum fuel economy. Accordingly, conventional venturis suffer the same restricting effect at or near maximum power requirements but to a lesser degree. It must be understood that such venturi restriction is not a problem at the lower engine speeds where even a half-sized venturi is adequate for slow moving engine pistons, but the problem becomes more and more critical at the higher engine speeds.

In order to control the desired re-opening of the secondary air valve 42, means are coupled to its actuating arm 48 in over-riding relationship to the aforedescribed control device including the piston 74. The over-riding control means, however, are coupled in sensing relationship to either one or both of the venturis 28, 31 and in turn are controlled by the venturi conditions as the undersized venturis begin to restrict the primary air requirements. Venturi depression or vacuum is clearly evident at lower engine speeds in the area of the venturi throat or restriction but becomes more marked as the venturi velocities increase with engine speed and power demands. Such venturi depression can, therefore, be sensed and harnessed by the aforementioned over-riding control means of the invention to re-open valve 42 to the correct extent and at the proper time to prevent starving the engine of air upon demand for maximum or near maximum power, as described in detail below.

One arrangement of such over-riding control device for the valve 42 is mounted in chamber or cylinder 69 of the control mechanism 58 and includes, in this example, opposed pistons 76 and 114, which are conected back to back by a slotted connecting rod 80 which also straddles the valve control arm 48, in the manner of the connecting rod 78 described above. The lower piston 76, as viewed in FIGURE 1, is biased by compressed coil spring 116 acting thereagainst to urge the upper piston 114 against an adjustably mounted stop 118. The biasing spring 116 serves to counter the weight of the pistons 76, 114 and connecting rod 80 and also to counter the venturi depression communicated to the spring chamber 120 of the cylinder 69, through conduit 122, fitting 129, and passage 123 of the carburetor block 11. Contact 124 of the connecting rod 80 is normally above valve arm 48 to permit freedom of motion during previously described deceleration, cruise, and moderate acceleration engine conditions, but yet with proximity within the range of the stroke of piston 76, so that connecting rod contact 124 can engage arm 48, depress it and open valve 42 upon maximum or near maximum demand for power.

If a greater venturi depression is required in certain app'ications, the conduit 122 can be coupled alternatively to the fitting 125 connected to the passage and connecting conduit denoted generally at 127 and leading to the throat or vena contracta of the inner or booster venturi 31. In most cases, the depression of the booster venturi 31 is about double that of the outer venturi 28. It is also contemplated in many applications at least, that, the manifold depression truncated means, including the ball check valve 128, can be omitted as a result of connection to the relatively larger depression area of the booster venturi 31.

The upper piston 114 of the over-riding secondary air control device is responsive, on the other hand, to manifold vacuum or depression in the upper chamber 126 of the cylinder 69 and the urging of venturi depression in its effort under substantially less than maximum power conditions counters upon piston 76 to move contact 124 and arm 48 downwardly to open secondary air valve 42. Th cylinder portion 126 communicates with manifold vacuum through passage 71 in control block 59, ball check valve 128 therein, vacuum conduit 130, and fitting 131. The fitting 131 is threadedly joined to carburetor block 11 where it joins a passage 133 extending downwardly through the carburetor block 11, air chute 12, throttle base 14, insulating block 15, where it joins the intake passage adjacent the intake manifold 16.

In the check valve 128, ball 132 is urged against its seat 134 by spring 136 in a direction permitting restricted flow toward the intake manifold 16 through the aforedescribed fluid control circuit and, in this example, with tension sufficient to require about 4 inches of mercury to lift ball 132 off its seat 134. As a result, a manifold depression of about 20 inches of mercury produces about 16 inches of mercury in the upper portion 126 of cylinder 69 which acts upon the upper piston 114. A bleed passage 138, however, is interposed between chamber 126 and check valve 128, and is drilled in the mechanism block 59 to its passage 71 forming part of the aforementioned fluid control circuit. The bleed passage 138 communicates air cleaner atmosphere to the above-described fluid control circuit and, in this example, is provided with such cross section as to eifect a further reduction of the mercury depression in chamber 126, for example, from about 16 inches to about 6 inches of mercury, to prevent hammering between piston 114 and stop 118 and to bleed off any leakage past ball check 128 at about 4 inches of mercury and below. The foregoing and following mercury readings are set forth for illustrative purposes in describing a particular engine and carburetor operation. They will vary depending upon engine and carburetor sizes, and particularly upon the various control components provided by the invention, the sizes and weights of which must be varied to meet specific applicative conditions. Therefore, such readings or depression values are given as an aid to an understanding of the invention but in no way should be construed as values to which the invention is restricted or limited.

The bleed passage 138 serves to uum to a point where hammering between piston 114 and stop 118 is minimized and also cooperates with check valve 128 under static conditions in bleeding off any inadvertent leakage past the ball 132 and its seat 134.

The ball check valve 128 serves as means for sealing off or closing the fluid control circuit for the over-riding control device '76114 at manifold depression, for example of less than 4 inches of mercury. In this respect check valve 128 serves to truncate or eliminate the application of manifold vacuum to the upper piston 114 of the overriding control device when the engine is operated at or near maximum power. At such times the venturi depression (which is then at or near its maximum value) is counterbalanced only by the lower piston biasing means or spring 116. The truncating means including check valve 128 thus provides complete dissolution of the vacuum or depression within chamber 126 even although manifold depression may approach 3 inches of mercury at high engine speeds notwithstanding the fact that the throttle plate is wide open for maximum power. The check valve spring 136 thus delimits the range of manifold depression, preferably those corresponding to maximum or near maximum engine power, whereat the overmodify manifold vacriding control device 76-114 can be actuated by the venturi depression (with counterbalancing manifold depression being removed or decoupled) to re-open the valve 42. In this example the ball check spring is preloaded to about 4" Hg which has been found to be the maximum depression of a single venturi arrangement. As alluded to above, a larger depression, about 8" Hg maximum, an he obtained for operation of its over-riding valve control 76-114, if desired, and the ball check spring 136 can be similarly preloaded.

In operation, upon maximum or near maximum demand for power, venturi depression is communicated to the lower piston cylinder portion 121 At the same time, the minimal manifold depression associated with major power demands permits the ball check valve 132 to close, whereupon substantially atmospheric pressure is established within the upper piston cylinder portion 126. Accordingly, the over-pressure in the latter urges piston 114 downwardly, causing the slotted connecting rod 81 to actuate arm 48 to re-open valve 62 to the extent permitted by biasing spring 116 and the communicated venturi depression operating on lower piston 76. This operation supplies secondary air via channel 24 to the carburetor throat path 26. It should be noted that the overriding control device 76-11 is ve y selective and prevents premature re-opening of valve 42, since the aforementioned venturi depression cannot, without adequate throttle opening, actuate the over-riding control device 76-114. On the other hand, a wide-open throttle condition without the maximum or near maximum venturi depression attendant with high engine speeds cannot actuate the control device 76-114 to re-open valve 42, as the venturi depression is then insufiicient to overcome the lower piston biasing spring 116.

As shown in FIGURE 1 of the drawings the carburetor 113 is provided with a primary, manifold-sensing, power enrichment valve 216. The primary valve 216 is coupled in communication with the intake manifold depression through channel 85, in the conventional manner and to the fuel bowl 166 in series with a secondary fuel enrichment means including metering valve rod 168 and metering block 162 described in greater detail below. The enrichment valve 216 thus serves as a timing mechanism to cause the secondary enrichment means to enrich the fuel-air mixture when engine power is called for at any engine speed by a considerable opening of the throttle plate 30. Owing to the necessity of compromise in conventional carburetors, a power enrichment valve, similar in certain respects to the valve 216, is provided with a compromised metering aperture similar to aperture 217. The compromised conventional aperture is sized too small for high speed acceleration and too large for low speed acceleration.

In my novel carburetor the aperture 217, however, is enlarged beyond that required for maximum power demand and other metering means forming part of the secondary fuel enriching means are utilized to control the enriching fuel supply at all engine speeds. Thus, for example, the considerable opening of the throttle prevents the formation of unnecessary and uneconomical, overrich fuel mixtures at low speed accelerations and overleaned mixtures at high speed acceleration for moderate and high speed accelerations.

Venturi depression can also be utilized in accord with another feature of the invention to control the operation of the valve 168 to regulate such auxiliary fuel flow through the valve 216 upon demand for maximum power. The auxiliary fuel control system and the secondary air control. system may also be coordinated so as to complement each other in maintaining a correct power mixture throughout the entire power range of the carburetor 11 It should be stressed, however, that venturi depression is of necessity, present during operating conditions requiring substantially less than full power and it is therefore necessary to provide suitable moderating means which will signal when full power is not required and restrict the operation of valve rod 168 or its equivalent, only to the times when maximum or near maximum power is required.

Therefore, novel means are disclosed for controlling and coordinating the influx of both secondary air and secondary fuel in a timed and coordinated response to venturi depression, together with novel means for moderating or restricting the influx of said air and fuel during less than full power requirements.

Referring now more particularly to FIGURES l and 2, one arrangement for so controlling power enrichment at higher speeds is illustrated and includes, in this example, a venturi sensing control mechanism 140, which is in operating principle similar to the over-riding control device 76-112 of the secondary air control mechanism 58. The control mechanism has a piston 142 in cylinder 144 biased toward a valve closed position of the metering valve rod 168 as shown in FIGURE 1 by spring 146 within cylinder portion 148 which communicates with venturl 28 depression through conduit 156 and carburetor block passages 151 and 123. The control mechanism 140 includes a second piston 152 in cylinder 154 havin g a chamber 156, which communicates through conduit 158 directly with chamber 126 portion of the overriding control device 76-114, via apertures 157, 159 in adjustable stop 118 which therefore transmits the manifold vacuum or depression as moderated and truncated by the previously described metered bleed 138 and ball check valve 128.

An additional novel feature of the invention in coordimating the operation of the secondary air control mechanism 58 and of the auxiliary fuel control mechanism is therefore evident. The cylinder 152 and associated components of the auxiliary fuel mechanism 140 are comparable to the upper half of the over-riding control device 144-126 of the secondary air mechanism 58, and function in a like manner to restrain the action of piston 142 until manifold depression arrives in this example at a predetermined 4 inches of mercury. The fuel control mechanism 140, includes a suitably apertured block 141, which is secured by screws 160 to fuel metering plate 162 (FIGURES 1, 4 and 5) which is sandwiched between conventional metering block 164 and fuel bowl 166 of the carburetor 10. Metering rod 168 is journaled rotatably in a bushing 17% mounted transversely in the control mechanism block 141 and intermediately of the block cylinders 144 and 152 in this example. The metering rod 168 thus extends with clearance into the aforementioned metering plate 162 and continues through a bronze valve body 172 as an outboard bearing and valving mechanism where it terminates within the confines of metering block 162 and fuel chamber 174, defined by the fuel bowl 166 and the lower end of the metering plate 162.

At the upper terminus of metering rod 168, a couple 176 is secured transversely thereto at its midpoint by bolt 178 (FIGURE 1). A connecting rod 180 links piston 154 to the adjacent end of the couple 176 by journal pins 182 and 184, respectively, while connecting rod 186 links piston 142 to the other end of the couple 176 by journal pins 188 and 190. Pistons 154 and 142 are therefore diametrically opposed across couple 176 so as to rotate metering rod 168 counterclockwise within valve body 176 in response to venturi depression or clockwise in response to an opposing intake manifold depression operating through conduit 130 and ball check valve 128 as previously described. Screws 192, 198 and locknuts 296, 202 are provided as adjustable means for stopping rotation of couple 176 and thus delimit the rotation of metering rod 168 within valve body 172. A cover 204, secured to block 141 by bolts 206 and 298, closes the outer ends of cylinder portions 143 and 156 and retains opposing spring 146 of the venturi depression-coupled piston 142. Dust cover 210, secured to block 141 by bolt 212, restrains metering rod 168 against lifting out of operating posi- 13 tion. Rippled line 214 indicates the fuel level in fuel bowl 166.

In this example, the valve body 172 is pressed into the metering block 162, where it seats against the aforementioned primary power enrichment valve 216 with the result that a sealed series flow fuel circuit is formed through both valves. The fuel enrichment valve 216 functions either to interrupt or to permit flow from metered valve body 172. The valve body 172 and the metering rod 168 cooperating therewith, on the other hand, are actuated by the auxiliary fuel control mechanism 140 to meter and control the flow through valve 216 when the latter is opened by moderate and high speed power demands.

The valve body 172 is partially bored for clearance around the fuel enrichment valve 216 and has a milled cavity 218 which communicates with fuel supply chamber 174 of the bowl 166 through metering hole 220 and cross hole 222 in metering rod 168. The upper portion of the valve body 172 has a vapor bleed hole 224 to permit the removal of vapors from the valve body 172 and to keep it filled with fuel. For low speed acceleration the accumulated cross section of the metering hole 220 of rod 168 and the vapor bleed hold 224, in this example, is only about one half the fiow capacity provided in conventional carburetors by their power enrichment valves which reduced cross section yields a drastically and desirably reduced flow of enriching auxiliary fuel during such low speed accelerations.

The valve body 172 is provided with a third fuel access channel 226 which is normally closed by the metering rod 168 as shown in FIGURE 1, during low speed accelerations. However, the metering rod 168 is provided in addition with a second, transversely extending metering hole 228 which is rotated out of alignment with access channel 226 by the biasing action of spring 146 upon piston 142. During low speed accelerations there is insufficient venturi depression communicated to cylinder portion 148 to rotate the metering rod 168 counterclockwise and thus its last-mentioned metering hole 228 remains out of alignment with the fuel access channel 226. As engine speed increases, venturi depression also increases as noted previously and is transmitted to chamber 148 via conduit 151). If the manifold vacuum or depression is less than about 4 inches of mercury, in this example, the venturi depression-coupled piston 142 is moved progressively inwardly against the biasing spring 146 to rotate couple 176 and metering rod 168 counterclockwise to align metered hole 228 increasingly with fuel access channel 226 thus to contribute additional auxiliary fuel flow as engine speed increases.

From the above description it can be seen that the auxiliary fuel control mechanism 140'cooperates with the over-riding secondary air control device 76-114 to control the influx of supplementary fuel and air, that such influx is in response both to the sensing of a predetermined venturi depression and the sensing of certain intake manifold conditions so that the power fuel-air admixture can be precisely varied to maintain an optimum fuel-air ratio at all engine speeds and power conditions.

An important advantage of this invention resides in the fact that metering rod 168 contains metered holes 220 and 228 and that by removal of cover 210, bolt 178 and pins 184 and 190, metering rod 168 is easily removed for inspection, replacement or calibration. Stop screw 192 can be retracted away from the pivoted couple 176 to delay the opening of fuel jet 228 or screw 192 can be advanced to where fuel jet 228 is partially aligned with fuel access hole 226 and thereby contribute a partial flow therethrough in conjunction with fixed metered holes 220 and 224 for a richer power mixture prior to the response of venturi sensing piston 142.

On the other hand, stop screw 194 can be advanced toward couple 176 to prevent complete alignment of metered hole 228 with fuel access hole 226 and to partially preclude the flow therethrough for a leaner power mixture. The stop screw 194 can also be retracted away from couple 176 to a point where alignment occurs between metered hole 228 and fuel access hole 226 at some less-than-maximum, engine speed and thereafter continued rotation of metering rod 168 by the control mechanism would again misalign hole 228 with access hole 226 to lean the power air-fuel mixture at extremely high engine speeds.

It will be understood that, by use of the principles involved in this invention, the venturis and intake-manifold depression-sensing components of the auxiliary air control mechanism 58 and the auxiliary fuel control mechanism 140 can be integrated, if desired, into a single unit controlling the flow of both such fuel and air to a carburetor in response to venturi depression as previously described.

In order to prevent the opening of secondary air valve 42 under cold engine conditions, means arranged in accord with the invention are coupled in this example to the actuating arm 48 of the air control valve 42, and to a conventional choke mechanism 229 (FIGURE 1) for inactivating the air valve 42 in its closed or nearly closed position until the engine warms up. As better shown in FIGURES 1 and 3, one form of such valve inactivating means includes an arrangement for the cam control of the valve 42 and means for decoupling the secondary air control device 74 and particularly its chamber portion 84 from the intake manifold circuit. The inactivating means, in this example, includes -a conventional choke mechanism 229 including a housing 230 therefor bolted to the side of the carburetor block 11 in the usual manner and containing the conventional temperature responsive bimetallic spring (not shown) and the usual vacuum line and heat tube (not shown). The conventional single operating arm of the choke 229 has been replaced by bell crank 232 having journals 234 and 236 on the outboard end of each arm and firmly affixed at its fulcrum to its supporting shaft 238, which is angularly displaced by operation of the choke mechanism 229. The usual choke rod 240 is pivotally secured to journal 234 of the bell crank 232 and to journal 242 of choke arm 244 which in turn is affixed to choke plate 246 in the usual manner for rotational displacement therewith. The choke shaft 246 is journaled on opposite sides of carburetor 10 in the usual manner and has a choke plate 248 aifixed to it by suitable fastening means (not shown).

In this arrangement, channel 250 of the intake manifold depression-coupling circuit (including conduit 82) intersects the choke shaft 246. The shaft 246 is provided with a transversely extending aperture 252 so as to maintain continuity of flow through the channel 250, but only when the choke plate 248 is rotated to its fully open position, as better shown in FIGURE 1. Thus, the intake depression channel 250 provides uninterrupted flow through the choke shaft aperture 252 to the conduit 82 when the choke plate 248 is wide open or nearly wide open. When the choke mechanism 229 rotates operating shaft 238 counterclockwise to raise choke rod 240, the choke arm 244 and choke shaft 246 will be rotated clockwise in the normal process of closing the choke plate 248 across carburetor primary air intakes 254. Simultaneously therewith the shaft aperture 252 is rotated out of alignment with the channel 250 thus interrupting the flow path to conduit 82 so that manifold vacuum can no longer be communicated to chamber portion 84 and springs 92 and 96 thereupon raise the connecting rod contact 86 out of engagement with the control arm 48 of valve 42. Valve 42 will therefore swing closed to choke the secondary air channel 24 under the'influence of spring 56. The aperture 252 in the choke shaft 246, remains out of alignment with the channel 250 throughout most of the choke closing operation and until choke plate 248 returns nearly to its wide open position thus deactivating piston 74 during the normal choking warm-up period of the associated engine.

Outer valve arm 256 fitted into a slot 258 milled across the outwardly protruding end of the valve shaft 46 and extends upwardly along the exterior surface of air chute enclosure 18. A cam shaft 262 is journaled through the enclosing wall 19 and supports outwardly thereof a sectorshaped cam 264 and operating arm 266 which is apertured at 268 near its outer end to receive bent portion of choke-actuated rod 270. The other bent end of the rod 270 is received in the journal 236 in the outboard end of the bellcrank 232. A yoke 272 is secured flush with arm 256 at 274 as by welding. The cam 264 is positioned generally between the yoke 272 and arm 256 so as to engage the inner edges thereof and limit the rotation of shaft 46 and the'motion of valve 42. A stop 276 is secured to the adjacent outer surface of the enclosing wall 18 and to delimit the counterclockwise angular displacement of the cam and cam arm 264-266 in order to prevent over-center action of the choke-actuated arm 270.

The cam 264 is shown in FIGURES 1 and 3 in a posi tion consistent with the fully wide open choke position of the plates 248 wherein valve 42 is free to open under the urging of either of the connecting rod contacts 86, 124 of the secondary control mechanism 58. A flat 278 is formed on earn 264 to provide clearance for the outer valve arm 256 into which the arm 256 moves as the valve 42 and its shaft 46 rotate to their open positions. However, during light engine accelerations, the aforementioned connecting rod contacts 36, 124 are both retracted away from the operating arm 48 and the valve spring 56 urges the valve 42 toward its closed position until the rotation of valve shaft 46 carrying with it arm 256 and the appended yoke 272 is interrupted by engagement of the yoke 272 with the surface of cam 264 as a stop to prevent a complete closing of the secondary air valve 42, as better shown in FIGURE 1A. This provides the aforementioned minimum or preset open position of the valve 42 found to be advantageous for the running of a hot engine during moderate accelerations.

However, the preset opening of valve 42 is undesirable for cold starting or the cold running of an engine, since the normal choking of the carburetor intakes 254 would induce uncarbureted air to enter the secondary air channel 24 and cause an undesirably over-lean mixture. Therefore, as choke shaft 238 rotates counterclockwise under the influence of cold temperature for the normal closing of the choke plate 248 as previously described, journal 236 on secondary arm of bell crank 232 also rotates counterclockwise to move rod 270 and arm 266 to the right which rotates cam 264 clockwise on shaft 262 until flat 280 is rotated parallel to edge of yoke 272. At the same time cam 264 is rotated clockwise against the inner edge of arm 256 to thereby rotate shaft 46 and valve 42 to a full closed position, at which position the valve 42 is locked while the choke is closed or nearly closed. All of this is accomplished without undue strain upon a conventional choke spring, since with engine 05, control mechanism contacts 86 and 124 are both retracted away from control arm 48 and spring 56 serves to assist in closing valve 42. Immediately after starting, the engine, the piston 74 of the secondary air control mechanism 58 cannot act to bind choke cam 264 since it is deactivated by the rotational displacement of choke shaft 246 to close off fluid control circuit 82, 25a during choke operation as previously described. The choke cam 264 likewise does not have to overcome the urging of the power piston 76 of the air control mechanism 58 during wide open throttle since such throttle opening would drop the pressure below offset choke plate 248 thus urging choke plate 248 toward its open position in the usual manner. Through connecting rod 240, the bell crank 232 and the connecting rod 2711, cam 264 is rotated out of engagement with auxiliary valve arm 256. Thus the valve 42 remains fully closed during cold engine conditions until the choke mechanism opens freely by thermostatic control or resistively by pressure differentials across the choke plate 248. Thereupon the valve 42 can be opened when the venturi depression reaches a value sufiicient to urge downwardly the piston 76 of the control mechanism 58 as previously described. It should be noted that if venturi depression does become operative, as described, depending on engine operating conditions, then the fuel metering control mechanism also becomes effective to enrich the power mixture during cold engine accelerations.

The aforedescribed secondary air and auxiliary fuel control mechanisms together with the novel throttle and choke mechanism of the invention provide optimum fuelair ratios regardless of engine power demands, i.e., during idling, various degrees of acceleration and deceleration, cruising conditions, and regardless of engine speeds and temperatures. The maintenance of optimum air-fuel ratios therefore promotes fuel economy at all engine speeds and power requirements, without sacrificing power. Rather, the carburetor of the invention increases the available speed and power of a given engine with which it is used. The automatic fuel-air ratio adjustment virtually eliminates the necessity for seasonal carburetor adjustment, and, in this connection, is especially advantageous in climates having wide temperature swings between night and day or from day to day.

Another important advantage of the invention is the substantial reduction of noxious engine exhaust gases, including carbon monoxide. Such gases result, of course, from improper or inefiicient combustion. Incomplete combustion of engine fuel and the attendant production of noxious exhaust gases are substantially reduced by the invention in that over-enrichment of conventional carburetors is prevented by controlling the introduction of both fuel and air at all engine speeds and power demands. Thus, the dangerous emission of such noxious gases can be controlled in confining or crowded areas, such as city trafiic, where such gases stem mainly from over-enriched idle and low-speed acceleration conditions.

From the foregoing it will be apparent that novel and efficient forms of carburetors and carburetor adjustments or adjusting means have been disclosed herein. It is to be understood that a certain feature or features of the invention can be utilized without a corresponding use of other or all of the features of the invention, depending upon a given application thereof. Therefore, while I have shown and described certain presently preferred embodiments of the invention and have illustrated presently preferred methods of practicing the same, it is to be distinctly understood that the invention is not limited thereto but may be otherwise variously embodied and practiced within the scope of the following claims:

I claim:

1. In a carburetor for an internal combustion engine and the like, said carburetor including an intake manifold, a throttle valve in a main airflow passage through the carburetor to the intake manifold, and combustible mixture generating means positioned in said main air passage on the opposite side of the throttle valve from said intake manifold, the combination comprising secondary air channel means coupled to said main airflow passage between the mixture generating means and said throttle valve, valve means mounted in said secondary air channel and movable to open and to close said secondary air channel to control the flow of secondary air therethrough, means for moving said valve between the open and closed positions thereof, said valve moving means being responsive to depressions of said manifold, said valve moving means including pressure sensitive motive means and conduit means coupled to said motive means and to said manifold for communicating said depressions thereto, a pair of unequal biasing members coupled in tandem to said motive means and disposed to oppose the manifold forces transferred to said motive means by said conduit means, and retainer means engaging said biasing members for applying the biasing forces thereof in seriatim to said motive means.

2. The combination according to claim 1 wherein said motive means include a piston and cylinder arrangement, said biasing members are compressed springs respectively, and said retainer means include a retainer member interposed between said springs and slidably mounted within said cylinder between a pair of stop members formed therein.

3. The combination according to claim 1 wherein said motive means include a piston and cylinder arrangement, the lighter one of said biasing members is supported by a housing therefor slidably mounted in said cylinder, said housing extending toward a retainer member interposed between said biasing members, said retainer member serving as a stop for said housing during a predetermined range of manifold depressions.

4. In a carburetor for an internal combustion engine and the like, said carburetor including an intake manifold, a throttle valve in a main airflow passage through the carburetor to the intake manifold, and combustible mixture generating means positioned in said main air passage on the opposite side of the throttle valve from said intake manifold, the combination comprising secondary air channel means coupled to said main airflow passage between the mixture generating means and said throttle valve, valve means mounted in said secondary air channel and movable to open and to close said secondary air channel to control the flow of secondary air therethrough, means for moving said valve means between the open and closed positions thereof, said valve moving means being responsive to pressure variations in said mixture generating means and to intake manifold depressions, said valve moving means including pressure sensitive motive arrangements coupled in parallel to said valve means, said arrangements being coupled to said mixture generating means and to said manifold, respectively, in pressure transmitting relation therewith.

5. The combination according to claim 4 wherein said mixture generating means include a venturi, and the associated one of said arrangements is coupled to the vena contracta thereof.

6. The combination according to claim 4 wherein said mixture generating means include an outer venturi and an inner venturi, and the associated one of said arrangements is coupled to the vena contracta of said inner venturi.

7. The combination according to claim 4 wherein that motive arrangement coupled to said mixture means includes a double-ended cylinder and piston, conduit means are coupled to an end of said cylinder adjacent one side of said piston and to said mixture means, and additional conduit means are coupled to the other end of said cylinder adjacent the other side of said piston and to said in take manifold to communicate pressure variations of said manifold to said other piston side to oppose said mixture generating means pressure variations.

8. The combination according to claim 7 wherein depression truncating means are coupled in said additional conduit means so that said mixture means motive arrangement is rendered operative by said mixture generating means at a low range of intake manifold depressions as predetermined by said truncating means.

9. The combination according to claim 8 wherein said truncating means include biased check valve means and bleed passage means coupled between said check valve means and said cylinder to facilitate relieving said cylinder during rapidly varying manifold pressures.

10. The combination according to claim 4 wherein said carburetor is provided with valved fuel supply means for enriching the air-fuel mixtures in the higher power operating ranges of an associated engine, said fuel supply means including a rotatably mounted metering valve having flow aperture means therein and movable to positions of misalignment, partial alignment and full alignment with a fuel passage forming part of said fuel supply means, and said metering valve is rotated by control means coupled to said mixture generating means for response to pressure variations therein.

11. The combination according to claim 10 wherein additional conduit means are coupled to said intake manifold and to each of said valve moving means and said metering valve control means so as to communicate intake manifold pressure variations thereto in opposition to said mixture generating means pressure variations.

12. The combination according to claim 11 wherein said mixture generating means include inner and outer venturis, and said valve moving means and said metering valve control means are coupled to the vena 'contracta of said inner venturi.

13. The combination according to claim 11 wherein said mixture generating means include inner and outer venturis, said valve moving means and said metering valve control means are coupled to the vena contracta of said outer venturi, and pressure truncating means are coupled in said additional conduit means so that said valve moving means and said metering valve control means are rendered operative by the depressions of said outer venturi at a relatively low range of manifold depressions as predetermined by said truncating means.

14. In a carburetor for an internal combustion engine and the like, said carburetor including an intake manifold, a throttle valve in a main airflow passage through the carburetor to the intake manifold, and combustible mixture generating means including at least one venturi positioned in said main air passage on the opposite side of the throttle valve from said intake manifold, the combination comprising valved fuel supply means for enriching the air-fuel mixtures in the higher power operating ranges of an associated engine, said fuel supply means including a rotatably mounted metering rod having flow aperture means therein and rotatable to positions of misalignment, partial alignment and full alignment with a fuel passage forming part of said fuel supply means, and said metering rod being rotated by control means coupled to the vena contracta of said venturi for response to pressure variations therein.

15. The combination according to claim 14 wherein a pair of pressure sensitive motive arrangements are coupled in opposition to said metering rod, one of said arrangements being coupled to said intake manifold and the other of said arrangements being coupled to said mixture generating means.

16. The combination according to claim 15 wherein pressure truncating means are coupled between said one arrangement and said manifold so that said other arrangement is rendered operative by the depression of said venturi means at a relatively low range of intake manifold depressions as predetermined by said truncating means.

17. The combination according to claim 16 wherein said pressure truncating means include biased ball-check means mounted in a channel coupling said cylinder arrangement and said manifold, and a bleed passage coupling said channel with the ambient atmosphere.

18. In a carburetor for an internal combustion engine and the like, said carburetor including an intake manifold, a throttle valve in a main airflow passage through the carburetor to the intake manifold, and combustible mixture generating means positioned in said main air passage on the opposite side of the throttle valve from said intake manifold, the combination comprising secondary air channel means coupled to said main airflow passage between the mixture generating means and said throttle valve, valve means mounted in said secondary air channel and movable to open and to close said secondary air channel to control the flow of secondary air therethrough, means for moving said valve between the open and closed positions thereof, said valve moving means being responl9 sive to depressions of said manifold, over-riding valve control means coupled to said secondary air valve means, said over-riding valve control means being responsive to depressions in said mixture generating means and in said intake manifold to reopen said secondary air valve means at a predetermined low manifold depression.

19. The combination according to claim 18 wherein said mixture generating means include at least one venturi mounted in the main flow passage of the carburetor, and said over-riding valve control means include a doubleended piston and cylinder arrangement, the cylinder on one side of said piston being coupled in communication with the throat of said venturi, and the cylinder on the other side of said piston being coupled through depression truncating means to said intake manifold so that said over-riding valve control means is rendered operative by venturi depression at a low range of intake manifold depressions as predetermined by said truncating means.

21). The combination according to claim 19 wherein said mixture generating means include an outer venturi and an inner booster venturi mounted substantially coaxially therein, and said cylinder at said one side of said piston is coupled to the throat of said inner venturi.

21. The combination according to claim 19 wherein said truncating means include biased check valve means, the biasing means therefore being directed and having a value so that manifold depressions of substantially the same ranges as said venturi depressions will not oppose the movement of said piston by said venturi depression.

22. The combination according to claim 19 wherein said cylinders are mounted in side-by-side relationship in a control block forming part of the mechanism for controlling said by-passing air valve means, and said valve means includes an operating arm extending transversely through openings in said block and adjacent said cylinders where said arm is engaged by slotted connecting rods in straddling relationship, said rods being coupled respectively to said pistons.

23. In a carburetor for an internal combustion engine and the like, said carburetor including an intake manifold, a throttle valve in a main airflow passage through the carburetor to the intake manifold, and combustible mixture generating means positioned in said main air passage on the opposite side of the throttle valve from said intake manifold, the combination comprising secondary air channel means coupled to said main airflow passage between the mixture generating means and said throttle valve, valve means mounted in said secondary air channel and movable to open and to close said secondary air channel to control the flow of secondary air therethrough, means for moving said valve between the open and closed positions thereof, said valve moving means being responsive to depressions of said manifold, said valve moving means including pressure sensitive motive means and conduit means coupled to said motive means and to said manifold for communicating said depressions thereto, a choke mechanism having a shaft extended across said conduit means to block the communication of said intake manifold depressions therethrough in the closed and partially closed positions of said choke mechanism, said choke shaft having a transversely extending aperture therein adjacent said conduit means, said aperture being alignable With said conduit means to communicate said manifold depressions therethrough when said choke shaft is disposed adjacent the fully open position of said choke mechanism.

24. The combination according to claim 23 wherein rotatably mounted cam means are mounted adjacent an operating arm for said secondary air valve means, said cam means being coupled through actuating rod and crank members to said choke mechanism for rotating said cam means thereby to a first position corresponding to the substantially open position of said choke mechanism, said cam means having a surface engageable with said actuating arm at said first position to maintain said secondary air valve means at a minimal partially open position, said cam means being rotated by said choke mechanism to a second position corresponding to the closed and partiallyclosed positions of said choke mechanism whereat said cam surface is rotated out of engagement with said valve actuating arm, and biasing means are coupled to said secondary air valve means to close said valve means at said second cam means position.

25. The combination according to claim 24 wherein said valve actuating arm includes a yoke portion which at least partially surrounds said cam surface, said cam surface engaging said yoke portion of the arm at said first cam means position to maintain said minimal open valve position, said cam surface engaging a second arm portion at said second cam means position to close said valve and to lock said valve in its closed position.

26. In a carburetor for an internal combustion engine and the like, said carburetor including an intake manifold, a throttle valve in a main airflow passage through the carburetor to the intake manifold, and combustible mixture generating means positioned in said main air passage on the opposite side of the throttle valve from said intake manifold, the combination comprising secondary air channel means coupled to said main airflow passage between the mixture generating means and said throttle valve, valve means mounted in said secondary air channel and movable to open and to close said secondary air channel to control the flow of secondary air therethrough, means for moving said valve between the open and closed positions thereof, said valve moving means being responsive to depressions of said manifold, valved fuel supply means for enriching the air-fuel mixtures in the higher power operating ranges of an associated engine, said fuel supply means including a rotatably mounted metering valve having flow aperture means therein and movable to positions of misalignment and partial alignment and full alignment with a fuel passage forming part of said fuel supply means, and said metering valve being rotated by control means coupled to said mixture generating means for response to pressure variations therein.

27. The combination according to claim 26 wherein said last-mentioned control means include a piston and cylinder arrangement, and biasing means are mounted in said cylinder and are coupled to said piston in opposition to said depressions communicated to said cylinder through conduit means coupled to said mixture generating means.

28. The combination according to claim 27 wherein a pair of said piston and cylinder arrangements are coupled in opposition to said metering valve, one of said piston and cylinder arrangements being coupled to said intake manifold and the other of said arrangements being coupled to the throat of venturi means forming at least part of said mixture generating means.

29. The combination according to claim 23 wherein said mixture generating means is at least one venturi mounted in the main flow passage of the carburetor, and over-riding valve control means are provided which includes a double-ended piston and cylinder arrangement, the cylinder on one side of said double-ended piston being coupled in communication with the throat of said venturi, and the cylinder on the other side of said piston being coupled through depression truncating means to said intake manifold so that said over-riding valve control means is rendered operative by venturi depression at a predetermined low range of intake manifold depressions as predetermined by said truncating means, and said one piston and cylinder arrangement is coupled to said over-riding means cylinder at said other piston end so as to be coupled through said truncating means to said intake manifold.

30. In a carburetor for an internal combustion engine and the like, said carburetor including an intake manifold, a throttle valve including a pivotally mounted throttle plate in a main airflow passage through the carburetor to the intake manifold, and combustible mixture generating means positioned in said main air passage on the opposite side of the throttle valve from said intake manifold, the combination comprising an idle fuel inlet channel opening into said airfiow passage adjacent said throttle plate, that portion of said throttle plate adjacent said idle fuel opening being disposed at an angle to the remainder of said plate, said throttle plate being so shaped that the edge of said plate remainder engages and the edge of said angled plate portion is spaced from, respectively, the adjacent inner surfaces of said main carburetor channel at the closed position of said throttle plate.

31. The combination according to claim 30 wherein said plate portion is angled toward its open position so that as said throttle plate is pivoted toward said open position said plate portion edge is moved more rapidly away from the adjacent inner surface of said carburetor channel than is said plate remainder edge from its adjacent inner surface.

References Cited UNITED STATES PATENTS 965,322 7/1910 Peterson 261-65 Stapelle 261-41 Heitger.

Aseltine.

Huber 261-63 Meyer 261-65 X Weigand et a1 261-69 Mallory 261-65 Jorgensen et al. 261-46 X Bracke 261-63 Weaving 261-69 X Nystrom et a1. 261-69 X Barnes 123-124 La Force 261-63 Serrugys 123-124 Arpaia 261-69 X Anderson 261-65 X HARRY B. THORNTON, Primary Examiner.

20 TIM R. MILES, Examiner. 

